Mobile information appliances such as a cellular telephone generally have 10˜12 keys in number to enter words with. In case of a language having 10˜12 characters in number, it is easy to enter words because a character can be allocated to a key. However, most languages have various and lots of characters, and it is impossible to allocate a character to a key. In addition, it is inconvenient to enter characters into small mobile information appliances such as a PDA because it has a full-size software-driven keyboard to enter words by means of pen-touching method.
FIG. 1a shows a keypad of cellular phone according to a Japanese standard for entering Japanese texts. As shown in FIG. 1a, the Japanese alphabet is distributed in sets of five letters to be allocated to keys, according to the configuration table of the Japanese alphabet. Each key represents a set of characters. For example, the characters of “” column, “”, are allocated to “1” key, and the characters of “” column, “”, to “2” key. The characters of “” columns are allocated to “3, 4, . . . ” keys, respectively. Currently, the common way to enter Japanese texts using such a conventional Japanese keypad is through the multi-tap method. For example, if a user wants to enter a word, “”, he or she has to press “2” key once for entering “”, press “1” key four times according to the order listed on the key for entering “”, and press “9” key five times according to the order listed on the key for entering “”. As a result, the entry of “” needs ten times of key presses.
FIG. 1b shows a keypad of a cellular telephone according to an international standard for entering English texts. The 26 characters are allocated to 10 keys. The common way to enter English texts using such a conventional English keypad is also through the multi-tap method.
FIG. 1c shows a keypad of cellular telephone in which Hebraic alphabet is allocated to 10 keys so that a user can enter Hebraic characters.
FIG. 1d shows a keypad of cellular telephone in which Thai alphabet is allocated to 10 keys so that a user can enter Thai characters.
FIG. 1e shows a keypad of cellular telephone in which strokes are allocated to 10 keys so that a user can enter simplified Chinese characters.
FIG. 1f shows a keypad of cellular telephone in which Bopomofo symbols are allocated to 10 keys so that a user can enter traditional Chinese characters.
FIG. 1g shows a keypad of cellular telephone in which Korean alphabet is allocated to 10 keys so that a user can enter Korean characters.
Currently, the common way to enter a text using the above-mentioned keypads is through the multi-tap method. However, the multi-tap method is very cumbersome and can cause a user to make mistakes on the character entry since groups of multiple letters are allocated on a limited number of keys and multiple letters are overlaid on each of these keys. To overcome these disadvantages, a single-tap method has been developed. As a single-tap method, there are disclosed T9 (http:// www.t9.com), eZi (http://www.zicorp.com), itap (http://www.mot.com/lexicus/html/itap.html), and for entering Japanese texts, POS (http://www.muchy.com). One feature of these methods is one tap (key press) for one letter.
FIG. 1h shows an embodiment according to the eZi method. The most important difference between the single-tap and the multi-tap method is related to whether or not to use a given dictionary for a given language. The single-tap method is based on an algorithm, which displays automatically the corresponding words after searching a given dictionary for a given language for combinations of the entered characters. For example of the eZi method, if a user, want to enter “boy”, he/she presses “1” key having letters “ABC” imprinted thereon for entering “b”, “6” key for entering “o”, and “9” key for entering “y”. When “b” is entered, the system searches a given dictionary using “b” as a search key, and then, when “o” is entered, “bo” is used as a search key. Finally, when “y” is entered, the system finds “boy”, as a word, in the dictionary, and the user selects and enters the word “boy”.
During the entering, nine (3×3×3) character combinations are generated from ABC, MNO, and WXY with the key entries. With the first key press, “ABC” is entered at once, and with the second key press “MNO” is entered at once, thereby displaying the possible combinations of letters in ABC×MNO, {AM, AN, AO, BM, BN, BO, CM, CN, CO}. Here, the desired character combination is “bo”. The system searches continuously the dictionary for the next character entry although there might be right words among the two-character combinations, and finally identifies the desired word. In the process, the character combinations associated with the key presses, which can be used as the beginning of the desired word, for example, “bo” can be selected and displayed continuously. Then, the system searches the dictionary in order to find all of the words, which include “bo” in the beginning of the word, and displays the resulting words. The user can identify and select the desired word among the words that the system speculates by oneself and displays.
FIG. 1i shows the POS system, which is a Japanese language calculation-input system according to the single-tap method. The algorithm is the same with the above-mentioned one.
As described above, there is provided the single-tap method instead of the multi-tap method, in order to seek the efficiency of character entry by allocating multiple letters to a limited number of keys of a small keypad. The single-tap method pursues the efficiency of character entry through the reduced number of times of key presses and an accuracy of character entry.
In a small keypad having a limited number of keys, multiple letters have inherently to be allocated to a key, and, therefore, the basic way to access a letter is a multi-tap method under the circumstances. However, the multi-tap method needs lots of key presses and has high possibility that a user may make mistakes on the character entry. On the other hand, the single-tap method can reduce the number of times of key presses, but has to establish a given dictionary for a given language in the system and to register new words continuously, such as vocabularies newly created by a user and abbreviations, in the dictionary. Besides, it is physically impossible to register all the vocabularies required in the rapidly developing information and telecommunication circumstances, such as names, internet addresses and homepage addresses, in the dictionary. In fact, if a vocabulary is not registered in the dictionary, a user has to use the multi-tap method at the same time in order to enter the vocabulary. Therefore, the single-tap method as a one-key-for-one-letter way has limitations and disadvantages which give the system high load due to lots of character combinations according to the entered multiple letters and dictionary-searching according to the character combinations.